Manhole covers have holes drilled two inches in diameter and are used when installing remote reading devices in the covers for water flow meters in water supply systems, or to provide filtered vent openings in manhole covers for sewage systems.
In the past manhole covers had to be delivered to an off-site shop and on-site location for drilling 2″ diameter holes to installing remote devices and vent holes. The drilling procedure requires two-inch diameter solid-bits. Transporting manholes was a time consuming, expensive and inconvenient task. The current approach is to use a hollow drill bit magnetically mounted on a semi-circular plate that is clamped on site to the manhole cover. The drilling press is similar to drill presses used for maintenance and construction of bridges, wherein the drill presses are secured by electromagnetics to metal bridge structures. The uneven surface of a manhole cover makes it impossible to effectively mount an electromagnetic drill press directly on the manhole cover. The semi-circular plate provides a smooth surface for magnetically holding a drill press on a manhole cover while the semi-circular plate is clamped to manhole cover.
Clamping the semi-circular plate to the manhole cover has proved difficult because the clamps can become detached during transport, storage and use. Consequently, when the plate and drill press arrive at the site, missing clamps cause substantial inconvenience.